Devices for exploiting the flue gas heat in the flue of a hot water boiler



Jan.-3, 1967 P. H. RANEBO 3,295,503

' DEVICES FOR EXPLOITING THE FLUE GAS HEAT IN THE FLUE OF A HOT WATERBOILER Filed Jan. 8, 1965 United States Patent Ofiice Patented Jan. 3,1957 3,295,503 DEVICES FOR EXPLOITING TIE FLUE GAS IEAT IN THE BLUE OF AHOT WATER BOILER Per Herman Ranebo, Rainge, Hassleholrn, Sweden FiledJan. 8, 1965, Ser. No. 424,249

Claims priority, application Sweden, Mar. 7, 1964,

2,884/ 64 3 Claims. (Cl. 122-20) This invention has for its object tomake it possible economically to exploit the flue gas heat in the flnesof hot water boilers for distributing hot water for instance to heatinginstallations. The invention is characterized in that at least part ofthe flue is surrounded by a jacket which together with the flue definesa space which has its ends connected to a hot water return conduit andto the hot water boiler, respectively, so that it will form part of thewater return conduit.

According to the invention, the device outlined in the foregoingconstitutes both an eflicient heat exchanger for exploiting the heatcontents of the flue gases and a device protecting the material in theflue, chimney and adjoining parts against overheating.

For better elucidation the invention will be described more in detail inthe following, reference being bad to the accompanying drawing whichdiagrammatically shows a vertical sectional view of a chimney extendingfrom a hot water boiler, and a conduit system mounted in the chimney forheat exchange between the flue gases and the return water to the boiler.

The flue 2 extends from the hot water 'boiler 1 horizontally into abrick base 3 with smoke box and smoke box door 4 and from said base 3vertically upwardly through the chimney 5. The flue 2 is of a relativelysmall diameter as compared with the space of the chimney, which in theexample shown is of a normal size for a small apartment house ordetached house whereby an amply dimensioned free space is obtainedbetween the inner side of the chimney and the flue 2 to accommodate anouter water tube 6 which is mounted in the chimney and surrounds theflue 2 in the manner of a water jacket throughout the greater part ofthe vertical length of the flue 2. The diameter of the outer water tube6 is so much larger than that of the inner flue 2 that a suflicientlywide gap remains between the twotubes for leading the return water backto the boiler. In the example shown the inner tube 2 has a diameter ofabout 15 cm. and the outer tube 6 a diameter of about 20 cm. The widthof the gap between the tubes then is about 2.5 cm., which has provedsuflicient in normal cases.

The water passage between the two tubes, which is of annular section, isclosed at the upper and lower ends and has these ends connected to thewater return conduit 7 from the hot water system and to the water returntube 8 leading to the boiler, respectively. The lower end of the waterconduit terminates at a level with the water return tube 8 and the upperend thereof at a level with or above the water return conduit 7 from theuppermost storey.

The outer water tube 6 can be supported at the lower end in a mannershown in the drawing on a shelf 9 which is built of bricks in thechimney or consists of holders secured therein. The seal between theupper and lower ends of the water tube 6 and the flue 2 is realized inthat an annular end wall plate 10 is welded in position about the flue 2and to the end of the water tube 6. According to the need, for instancein multi-storeyed buildings, the water tube 6 can be divided intosections, each section being connected and sealed in the mannerdescribed, with the diiference, however, that an upper section 6' isconnected at its lower end to the snbjacent section 6 by means of a tubeinstead of to the boiler. Such a connection is shown at 11 in the tophalf of the drawing where the shelf 9 for supporting the adjoining endsof the two water tube sections 6, 6' is disposed.

To permit emptying of the outer water tube 6 independently of the waterreturn tube 8 to the boiler, the lower end of the water tube can beconnected to a separate emptying conduit equipped with a valve (notshown).

In practical use the device described in the foregoing has proved veryeflicient in point of good fuel economy but it has also proved soeffective as a heat protecting means around the flue that it is evenpossible to dispense with a brick chimney.

What I claim and desire to secure by Letters Patent is:

1. In combination with a hot water distribution system, means forexploiting the flue gas heat comprising a hot water boiler,

a flue passing through a chimney structureand connected to said hotwater boiler to receive heat therefrom,

a jacket surrounding at least a part of said flue and defining togetherwith said flue a water conduit to permit the return to the boiler ofwater in the hot water system,

a hot water return conduit connected from the hot water distributionsystem to the upper part of said water conduit,

and a water return pipe connected from said hot water boiler to thelower end of said water conduit whereby the return water from the hotwater system is preheated by the flue gas heat before arrival in theboiler.

2. The combination as claimed in claim 1, wherein said jacket is theouter covering for said flue, being the chimney structure over the partof said flue surrounded by said jacket.

3. The combination as claimed in claim 1, wherein said chimney structureis formed of brick-like material around the outside surface of saidjacket.

References Cited by the Examiner UNITED STATES PATENTS 121,973 12/1871Till 122-20 357,992 2/ 1887 Hewitt 122-20 X 704,009 7/1902 Ebersole122-20 866,842 9/ 1907 Comstock.

895,669 8/1908 Ogden 122-439 X 1,458,876 6/1923 Confer 122-20 CHARLES I.MYHRE, Primary Examiner.

1. IN COMBINATION WITH A HOT WATER DISTRIBUTION SYSTEM, MEANS FOREXPLOITING THE FLUE GAS HEAT COMPRISING A HOT WATER BOILER, A FLUEPASSING THROUGH A CHIMNEY STRUCTURE AND CONNECTED TO SAID HOT WATERBOILER TO RECEIVE HEAT THEREFROM, A JACKET SURROUNDING AT LEAST A PARTOF SAID FLUE AND DEFINING TOGETHER WITH SAID FLUE A WATER CONDUIT TOPERMIT THE RETURN TO THE BOILER OF WATER IN THE HOT WATER SYSTEM, A HOTWATER RETURN CONDUIT CONNECTED FROM THE HOT WATER DISTRIBUTION SYSTEM TOTHE UPPER PART OF SAID WATER CONDUIT, AND A WATER RETURN PIPE CONNECTEDFROM SAID HOT WATER BOILER TO THE LOWER END OF SAID WATER CONDUIT